Electricity is the cornerstone of modern life and also a driving force for economic development. In the traditional industries, such as printing plants, textile factories, steel mills, petrochemical plants, etc., as well as in the emerging high-tech industries, such as semiconductor plants, LCD panel plants, etc., electricity is invariably the power for driving production lines and various equipment. In addition, almost every household needs electricity for items such as lamps, electric water heaters, televisions, air conditioners, refrigerators, etc. in order to lead a quality life.
However, with the depletion of available energy and the growing demand for electricity, governments all over the world have advocated that either electricity bills be charged according to a time-of-use rate or power companies buy electricity from the private sector to reduce the load on the power companies and to lower the pressure of the need to build more power plants. Apart from that, many households have their own solar or wind power generators installed to produce electricity for their own use, thereby reducing electricity expenses. Nevertheless, whether people sell excessive electricity to power companies or produce electricity by themselves, additional problems follow.
In regard to the situation where people sell excessive electricity to the electric system of a power company, please refer to the illustration of FIG. 1A. After people use their own power generation equipment 11 to produce electricity, the generated electricity is transmitted to a power company circuit 15 through a first electricity meter 13. Then, the power company transmits electricity through a second electricity meter 17 to a household circuit 19 for use by electric appliances in people's home. Thus, people can sell the electricity generated by the power generation equipment 11 to the power company for the purpose of reducing electricity fees. However, a power company, when purchasing electricity, generally provides different purchase prices corresponding to different time periods of a day. When the purchase price is below the market price of mains electricity, the electricity generated by the power generation equipment 11 cannot be directly used in the household circuit 19 but still has to be sold to the power company, and the power company will then transmit electricity back to the household circuit 19. This results in a net loss for people buying and selling electricity at different prices. In regard to the situation where people produce and use their own electricity, please refer to the illustration of FIG. 1B. When people use their own power generation equipment 21 to generate electricity, the electricity can be directly transmitted from the power generation equipment 21 to the household circuit 23 for use by the electric appliances in people's home. When the electricity generated by the power generation equipment 21 is insufficient to be supplied to the electric appliances in people's home, the household circuit 23 receives electricity from a power company circuit 27 through an electricity meter 25. In this way, people's electricity expenses can be significantly reduced. However, even though people do not stay home all day, they cannot sell the electricity generated by the power generation equipment 21 back to the power company when power consumption at home is relatively low. In other words, the electricity generated by the power generation equipment 21 either is not always being used or is not in use at all. In the long run, the electricity generated by the power generation equipment 21 is wasted, which lacks economic efficiency.
Hence, it is an important issue nowadays to design an electricity utilization method which combines the advantages of the aforesaid two cases in order to enable stable and adequate supply of electricity and reduction in power waste.